The present invention relates to seat suspension systems and more particularly to an improved seat suspension system, having means for dampening vertical seat movement, for reducing the shock transmitted through the seat to an operator when the seat "bottoms out" when operating an off-road vehicle on bumpy and uneven terrain.
It is known to provide seat suspension systems which dampen vertical seat movement in response to vehicle motion. It is also known and common to provide a fixed amount of vertical dampening.
In off-road vehicles such as lawn and garden tractors, conventional seat suspension system consists of at least one spring between the seat and the tractor for cushioning the force trasmitted to an operator sitting in the seat. Due to space, cost and material limitations, these conventional seat suspensions normally are adjusted and fixed to provide a soft ride on relatively even and non-bumpy terrain. Unless extreme drops or sharp rises were encountered by the vehicle, the operator experienced little discomfort. In instances when the vehicle encountered chuck holes in uneven terrain or curbs, the seat suspension system proved unable to satisfactory prevent substantial vertical movement of the suspension. Sometimes, in fact, this substantial vertical movement caused the seat suspension system to "bottom out" by exceeding the limit of vertical travel therein. The conventional suspension system is unable to satisfactorily absorb the sudden force generated by the "bottoming out" and thus transmitted it through the seat to the vehicle operator resulting in a sudden jolt to the operators body.
In a further effort to reduce some of the sudden force generated by the seat "bottoming out", rubber bumpers were mounted between the vehicle and the seat suspension system, as disclosed in U.S. Pat. No. 4,258,896. While rubber bumpers did some what reduce the sudden jolt associated with "bottoming out" and thus, the shock experienced by the operator, they did not prove to be fully satisfactory.
Additional efforts to solve the "bottoming out" problem resulted in the installation of expensive shock absorbers or other complex hydraulic systems. Examples of such prior seat suspension systems are disclosed in U.S. Pat. Nos. 4,382,573 and 4,384,700. While the shock absorbers and complex hydraulic systems did significantly reduce the shock transmitted to the operator, their installation on small lawn tractors has proved to be unfeasible due to cost and space limitations.
Thus, the vehicle manufacturer has had to compromise his seat suspension design between providing a softer ride during normal vehicle operations relative to reducing the vertical acceleration which resulted in the uncomfortable sudden shock when the seat "bottomed out". Because of the uncomfortable shock experienced by the operator when the seat "bottoms out", attenuation springs were selected which provide a less comfortable ride during normal vehicle operations in order to reduce the uncomfortable sudden shock when the vehicle encountered severe drop offs or rises.
Accordingly, there is a need for an improved seat suspension system for an off-road vehicle such as a small lawn and garden tractor or the like, which significantly reduces the force transmitted to the vehicle operator causing the seat suspension to "bottom out" when encountering bumpy terrain including chuck holes or curbs.